KR20070118289A - Transmission of signalling information in an ofdm communication system - Google Patents

Abstract

An Orthogonal Frequency Division Multiplexing, OFDM, transmitter comprises a signalling data generator (113) which generates a set of data symbols indicative of physical layer characteristics of data transmissions from the OFDM transmitter (100). A first symbol generator (115) and second symbol generator (117) generates a first and second OFDM signalling symbol by allocating the set of data symbols to subcarriers. The allocation of the physical layer data symbols to subcarriers is different for the first OFDM signalling symbol and the second OFDM signalling symbol. A data packet generator (105) and transmitter (101) generate a data packet and transmit this to an OFDM receiver (300). The OFDM receiver (300) determines the physical layer data symbols by combining the data symbols of corresponding subcarriers of the first and second OFDM signalling symbols and uses the resulting information to decode the user data of the data packet.

Description

Transmission of signaling information in PFDM communication system {TRANSMISSION OF SIGNALLING INFORMATION IN AN OFDM COMMUNICATION SYSTEM}

The present invention relates to the communication of signaling information in an OFDM communication system, and more particularly, to the communication of signaling information related to physical layer characteristics in an IEEE 802.11 communication system, but is not limited thereto.

In recent years, wireless data communication in home and business environments is becoming more and more common, and the number of wireless communication systems has been designed and adopted to increase. In particular, the use of wireless networking has become widespread, and wireless network standards such as IEEE 802.11a and IEEE 801.11g have become commonplace.

The need to increase data rate, communication capacity and quality of service has led to continued research, and new technologies and standards have been developed for wireless networking. One such standard is the IEEE 801.11n standard currently under development. IEEE 801.11n is expected to operate in the 2.4 GHz or 5 GHz frequency spectrum and guarantees a data rate of about 100 Mbps or more on top of the MAC layer. IEEE 801.11n will use a number of techniques similar to the earlier developed IEEE 801.11n and IEEE 801.11g standards. Standards are broadly compatible with many of the features of previous standards, allowing reuse of technology and circuits developed for them. For example, as in previous standards IEEE 801.11a and IEEE 801.11g, IEEE 801.11n will use Orthogonal Frequency Division Multiplex (OFDM) modulation for transmission over the air interface.

In addition, in order to improve efficiency and achieve high data rates, IEEE 801.11n is planned to introduce a number of advanced technologies. For example, IEEE 801.11n communication is typically expected to be based on multiple transmit and receive antennas. Furthermore, rather than merely providing diversity from spatially separated transmit antennas, IEEE 801.11n utilizes a transmitter having at least partially separate transmit circuitry for each antenna, so that other sub-signals can be transmitted from each antenna. Make sure The receivers receive signals from the plurality of receive antennas and perform joint detection considering the number and individual characteristics associated with each of the plurality of transmit antennas and receive antennas. In particular, IEEE 801.11n supports multiple-transmit-multiple-receive (MTMR), which utilizes multiple input multiple output (MIMO) channel characteristics to improve performance and throughput. The introduction of the antenna concept is anticipated.

To enable or facilitate reception, the IEEE 802.11a / g standard, as well as all IEEE 802.11n proposals, include a physical layer preamble in which every data packet contains well-known data that facilitates receiver gain setting, synchronization, and channel estimation. Prescribe what precedes it. In addition, a dedicated OFDM symbol that carries the physical layer signaling required for decoding the data packet is included. This information includes, among others, the information of the modulation scheme, the coding rate and the packet length for the data packet. This signaling is known as the SIG field. Since the IEEE 802.11n receiver requires information related to multiple antennas, the signaling field is enhanced for IEEE 802.11n and is generally referred to as SIG-N. The SIG-N field is communicated as a QPSK symbol on the subcarrier of the dedicated SIG-N field OFDM symbol.

In particular, SIG-N mapping (QPSK) is an implementation of the IEEE 802.11n proposal (Cenk Kose, Bruce Edwards, "WWiSE Proposal: High throughput extension to the 802.11 Standard", IEEE document number 11-05-0149-02-000n). Defined in the context.

In such a system, no signaling information is available prior to transmission of the SIG-N field, so the receiver must be able to decode this field without any previous information about its nature (this is necessary for compatibility reasons).

In addition to providing high data rate services, IEEE 802.11n is also expected to be used in a variety of applications with different requirements and characteristics. For example, IEEE 802.11n can be used for lower data rate applications such as mobile voice (VoIP) and mobile multimedia streaming over the Internet protocol for portable devices. Although these applications have low data rates, they are required to be accessed over large areas and it is desirable for IEEE 802.11n cells to have as wide a coverage area as possible.

To extend the range of IEEE 802.11n cells, a low data rate robust mode has been proposed that increases the range by utilizing the potential of the MIMO configuration.

Some proposed modes use space time block code (STBC) in combination with low order constellation Binary Phase Shift Keying (BPSK) to provide robust communication at lower signal-to-noise ratios. In another proposal, range extension is achieved by the efficient use of beamforming techniques.

However, one problem with these low boost modes is that the range extension applied to the user data appears to be in a range that exceeds that achieved for an OFDM symbol containing a SIG-N field. To overcome this mismatch, it has been proposed to introduce an optional simple repetition of the SIG-N field so that the OFDM symbol is transmitted twice.

This approach can increase range by providing 3dB signal-to-noise ratio improvement. However, this extension is advantageous, but not optimal and in some situations limits the effective coverage area of an IEEE 802.11n cell.

Therefore, an improved OFDM communication system is advantageous and in particular a system that allows increased range, improved compatibility between user data and signaling transmissions, lower complexity and / or improved performance.

Accordingly, the present invention seeks to alleviate, reduce or eliminate one or more of the above mentioned disadvantages, alone or in any combination.

According to a first aspect of the present invention, there is provided an apparatus, comprising: means for generating a data symbol set indicative of a physical layer characteristic of a data transmission from an OFDM transmitter; First symbol generation means for generating a first OFDM signaling symbol by assigning a data symbol set to a subcarrier of the first OFDM signaling symbol; Second symbol generating means for generating a second OFDM signaling symbol by allocating a data symbol set to a subcarrier of a second OFDM signaling symbol, wherein the allocation of the data symbol set to a subcarrier comprises a first OFDM signaling symbol and a second OFDM signaling. Different for symbol-; And transmitter means for transmitting a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol.

The present invention allows for improved communication of physical layer characteristic data. Increased range is obtained, allowing for improved cell coverage, for example. In particular, frequency diversity is utilized to allow transmission of signaling information with greater distance and / or improved reliability. In particular, in many communication systems, an improved correspondence between the range provided by the signaling information and the user data can be achieved.

In particular, the second symbol generating means provides an assignment of the data symbol set to the subcarrier different from that of the data symbol set by the first symbol generating means. Therefore, the allocation of data symbol sets to subcarriers is different for the first OFDM signaling symbol and the second OFDM signaling symbol.

According to an optional feature of the invention, the first symbol generating means is arranged to assign a first subset of data symbols to a first subset of subcarriers of the first OFDM signaling symbol, the second symbol generating means being a data symbol set And assign a first subset of to the second subset of subcarriers. This allows for low complexity and improved performance, in particular allowing efficient utilization of frequency diversity. The first and second subsets of subcarriers are subsets of unequal subcarriers.

According to an optional feature of the invention, the first symbol generating means is arranged to assign a second subset of data symbols to a second subset of subcarriers of the first OFDM signaling symbol, the second symbol generating means being a data symbol set And assign a second subset of to the first subset of subcarriers. This allows for low complexity and / or improved performance.

According to an optional feature of the invention, the first and second subsets of subcarriers are non-overlapping. No subcarrier of the first subset of subcarriers is included in the second set of subcarriers. This allows for improved performance and especially improves frequency diversity.

According to an optional feature of the invention, the second symbol generating means is arranged to assign a first subset of data symbols to a subcarrier having a predetermined offset with respect to the first subset of carriers. This allows for low complexity and / or efficient performance.

According to an optional feature of the invention, the second symbol generating means comprises a data symbol of the first subset of data symbols assigned to the subcarrier n by the first symbol generating means, the subcarrier number n + N (where N is a predetermined value). To assign a subcarrier to a data symbol. This allows for low complexity and / or efficient performance.

According to an optional feature of the invention, the first symbol generating means is arranged to include an indication of the presence of the second OFDM signaling symbol in the first OFDM signaling symbol. This allows for efficient performance, or improves backward compatibility, or facilitates communication in communication systems employing receivers and / or transmitters with other capabilities.

According to an optional feature of the invention, the message comprises an OFDM user data symbol, the data symbol set indicating a physical layer transmission characteristic for the OFDM user data symbol. This provides high performance or facilitates implementation.

According to an optional feature of the invention, the transmitter means is arranged to transmit a message on a plurality of transmit antennas. This improves performance. In particular, the first and second OFDM symbols can be transmitted using a space time code such as an Alamouti code or using a beamforming approach.

According to an optional feature of the invention, the first symbol generating means is arranged to include in the first OFDM signaling symbol an indication of the allocation of the data symbol to the subcarrier.

This improves performance or reduces complexity. The assignment corresponds to the assignment of the first OFDM signaling symbol and / or the second OFDM signaling symbol.

According to an optional feature of the invention, the OFDM transmitter is an IEEE 802.11 transmitter. The transmitter is in particular an IEEE 802.11a, IEEE 802.11g or IEEE 802.11n transmitter. The present invention provides particularly good performance in IEEE 802.11 communication systems and is compatible with the standards and proposals for these systems. In particular, for IEEE 802.11n systems, the range for signaling information is effectively increased, thereby providing an improved response to the attainable range for user data.

According to a second aspect of the present invention, there is provided an OFDM receiver for receiving a signal from an OFDM transmitter, the OFDM receiver comprising: means for receiving a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol—first OFDM The signaling symbol includes a set of data symbols representing physical layer characteristics of a data transmission from an OFDM transmitter assigned to a subcarrier of the first OFDM signaling symbol, and the second OFDM signaling symbol is a data symbol assigned to the subcarrier of the second OFDM signaling symbol. A set of data symbol sets different for the first carrier and the second OFDM signaling symbol; And means for receiving the data symbol set by combining the data symbol set of the first OFDM signaling symbol and the second OFDM signaling symbol.

The combination is a simple selective combination, for example, data is decoded from the appropriate subcarrier of either the first OFDM signaling symbol or the second OFDM signaling symbol depending on which subcarrier has the best signal to noise ratio.

The present invention allows for improved communication of physical layer characteristic data. Increased range is obtained, allowing for improved cell coverage, for example. In particular, frequency diversity is utilized to allow transmission of signaling information over wider distances or with improved reliability. In particular, in many communication systems, an improved correspondence between the range provided by the signaling information and the user data can be achieved. Obviously, the features described with reference to an OFDM transmitter can equally be applied to an OFDM receiver.

According to an optional feature of the invention, the receiving means is arranged to combine the data symbol set of the first OFDM signaling symbol and the second OFDM signaling symbol by the maximum ratio combination. This improves performance.

According to an optional feature of the invention, the OFDM receiver further comprises means for detecting the presence indication of the second OFDM signaling symbol in the first OFDM signaling symbol, the receiving means being arranged to receive the data symbol set in response to the detection. . In particular, the receiving means is arranged to receive the first set of data symbols without consideration of the second OFDM signaling symbol when no presence indication of any second OFDM signaling symbol is detected in the first OFDM signaling symbol.

This facilitates communication in a communication system that eliminates efficient performance, or improves backward compatibility, or employs receivers and / or transmitters with other capabilities.

According to a third aspect of the present invention, there is provided a method, comprising: generating a data symbol set indicative of a physical layer characteristic of a data transmission from an OFDM transmitter; Generating a first OFDM signaling symbol by assigning a data symbol set to a subcarrier of the first OFDM signaling symbol; Generating a second OFDM signaling symbol by assigning a data symbol set to a subcarrier of a second OFDM signaling symbol, the allocation of the data symbol set to a subcarrier being different for the first OFDM signaling symbol and the second OFDM signaling symbol -; And transmitting a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol.

According to a fourth aspect of the present invention, there is provided a method, comprising receiving a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol, wherein the first OFDM signaling symbol is data from an OFDM transmitter assigned to a subcarrier of the first OFDM signaling symbol. A data symbol set indicative of a physical layer characteristic of the transmission, wherein the second OFDM signaling symbol comprises a data symbol set assigned to a subcarrier of the second OFDM signaling symbol, and the allocation of the data symbol set to the subcarrier Different for the signaling symbol and the second OFDM signaling symbol; And receiving a data symbol set by combining a data symbol set of a first OFDM signaling symbol and a second OFDM signaling symbol.

These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiments described below.

Embodiments of the invention will be described with reference to the drawings, by way of example only.

1 illustrates an orthogonal frequency division multiplexing, OFDM transmitter in accordance with some embodiments of the present invention.

2 illustrates an example of data symbol allocation of an OFDM signaling symbol, in accordance with some embodiments of the present invention.

3 illustrates an OFDM receiver in accordance with some embodiments of the present invention.

4 illustrates an example of a data packet structure for transmission in an IEEE 802.11n system, in accordance with some embodiments of the present invention.

5 illustrates an example of a data packet structure for transmission in an IEEE 802.11n system, in accordance with some embodiments of the present invention.

6 shows a simulation result for error performance for an OFDM system according to the described embodiment.

The following description focuses on embodiments of the present invention applicable to technical specifications and suggestions for IEEE 802.11 communication systems and in particular IEEE 802.11n communication systems. However, it is apparent that the present invention is not limited to this application and can be applied to many other OFDM communication systems including, for example, other IEEE 802.11 communication systems.

1 illustrates an OFDM transmitter 100 in accordance with some embodiments of the present invention.

OFDM transmitter 100 includes a transmitter 101 arranged to transmit an OFDM signal in accordance with technical specifications for a communication system. In a particular example, OFDM transmitter 100 is an IEEE 802.11 transmitter coupled to antenna 103.

The transmitter 101 is further coupled to a data packet generator 105 that generates a data packet that is fed to the transmitter 101 for transmission. In particular, the data packet generator 105 generates a data packet comprising a plurality of signaling OFDM symbols and a plurality of user data symbols.

The data packet generator 105 is coupled to the user data symbol generator 107 which is further coupled to the user data source 109. In a particular example, the user data source 109 is an internal source, but it is apparent that the data to be transmitted may be received from any physical, logical or functional external or internal entity.

The user data symbol generator is further coupled to a transmission controller 111 that controls the transmission characteristics of the transmitted signal. In particular, other features and modes may be used for transmission, in accordance with the IEEE 802.11 specification. Specifically, other forward error correction schemes, modulation schemes, and transmission modes are used for the transmission of data packets, and the transmission controller 111 is arranged to select the desired parameters and feed them to the user data symbol generator 107.

In response, the user data symbol generator 107 generates an OFDM symbol by applying the selected error coding and modulation scheme to the user data received from the user data source 109. Specifically, the user data symbol generator 107 selects the appropriate data symbol by encoding data from the user data source and selecting the appropriate constellation point from a particular constellation for each subcarrier of the OFDM symbol. For example, in some modes, user data symbol generator 107 applies half rate convolutional encoding and generates QPSK symbols for each subcarrier, while in other low-boost modes, user data symbol generator 107 is configured to perform the < RTI ID = 0.0 > Apply half rate convolutional encoding to generate BPSK symbols for each subcarrier.

The transmission controller is further coupled to the signaling data generator 113. The signaling data generator 113 generates a set of data symbols representing the physical layer characteristics of the data transmission from the OFDM transmitter 100. In particular, the signaling data generator 113 generates a data symbol set that defines the transmission parameters and characteristics that have been applied to the user data by the user data symbol generator 107. Therefore, the data symbol set further identifies forward error correction coding and symbol constellations used, and further includes information of other transmission parameters that affect physical layer communication, such as, for example, the duration of the data packet.

In a particular example, the signaling data generator 113 generates a SIG or SIG-N field according to the specifications for the IEEE 802.11 communication system.

It is apparent that the physical layer is the lowest layer of the seven layer Open System Interconnection (OSI) or similar network model. The physical layer provides a means for activating and using a physical connection, in this case a wireless communication link for bit transmission. In other words, the physical layer provides a procedure for delivering individual bits across a physical medium.

The signaling data generator 113 is coupled to the first symbol generator 115 and the second symbol generator 117 from which the data symbol set is fed from the signaling data generator 113. In the example of FIG. 1, signaling data generator 113 generates a set of data symbols as QPSK symbols ready for transmission on individual OFDM subcarriers.

The first symbol generator 115 generates a first OFDM signaling symbol by assigning the received data symbol to a subcarrier of the first OFDM signaling symbol. Specifically, the first symbol generator 115 simply selects a subcarrier for each data symbol in the data symbol set according to a predetermined rule or table. For example, a single data symbol may be used to identify the applied forward error coding rate, which symbol may be predefined to be transmitted in subcarrier number N, so to speak.

Similarly, second symbol generator 117 generates a second OFDM signaling symbol by assigning the received data symbol to a subcarrier of the second OFDM signaling symbol. Similarly, the second symbol generator 117 can simply select a subcarrier for each data symbol in the data symbol set according to a predetermined rule or table. However, the assignment of data symbols is different for the first symbol generator 115 and the second symbol generator 117, so that at least some data symbols of the data symbol set are in different subcarriers of the first and second OFDM signaling symbols. Will be allocated.

The first symbol generator 115 and the second symbol generator 117 are further coupled to the data packet generator 105 which is fed to the first and second OFDM symbols. The data packet generator 105 then proceeds to generate a data packet including the first and second OFDM symbols as well as the user data OFDM symbols received from the user data symbol generator 107. In a particular example of an IEEE 802.11 transmitter, the data packet generator 105 further inserts a preamble of known data to facilitate reception, in particular to facilitate initial gain setting, synchronization and channel estimation by the receiver.

The generated data packet is fed to a transmitter 101 which proceeds to transmit OFDM symbols. In particular, the transmitter 101 performs an inverse Discrete Fourier Transform (iDFT) on the OFDM symbol and upconverts and amplifies the resulting signal as will be apparent to those skilled in the art.

Therefore, in the transmitter of FIG. 1, the physical layer signaling data symbol is transmitted twice using another OFDM signaling symbol. In addition, the allocation of data to different subcarriers is varied between two different signaling symbols, resulting in a reliability improvement over the 3 dB gain that can be obtained by conventional retransmission. Specifically, this approach allows data packets to be transmitted when the effective range for signaling information is substantially extended. In particular, in frequency selective fast fading channels typical for many applications of IEEE 802.11 systems, significant improvements of typically 30-35% can be achieved.

Specifically, the described transmitter provides improved transmission of the SIG-N field, which provides a longer range than the IEEE 802.11 robust boost range for transmission of user data. Therefore, the transmitter allows the coverage to be limited by the range of user data transmission rather than the range of signaling information contained in the data packet. This greatly increases coverage of 802.11 cells and improves reliability of communication.

It is apparent that any suitable mechanism, algorithm or criterion for allocating data symbols to subcarriers may be used unless the assignments are the same for the first and second OFDM signaling symbols.

In some embodiments, the first and / or second OFDM signaling symbol further includes an indication of allocation of data to another subcarrier. This can be used by the receiver when decoding the received data.

In some embodiments, the assignment may be based on, for example, a priori channel knowledge information. For example, in a closed loop scenario, the assignment can be continuously adapted to the current conditions. Alternatively or additionally, the receiver may feed back information that may be used to modify the allocation of data to the subcarrier.

In the particular example of FIG. 1, the first symbol generator 115 assigns a first subset of data symbols to a first subset of subcarriers of the first OFDM signaling symbol, whereas the second symbol generator 117 is identical. Allocates data symbols to different subcarrier subsets. In addition, a low complexity implementation can be obtained by the second symbol generator 117 which assigns data symbols to subcarriers having a predetermined offset relative to the assignment by the first symbol generator 115.

For example, if the first subset contains 10 data symbols, the first symbol generator 115 assigns them to subcarriers N, N + 1, N + 2, ..., N + 9. The second symbol generator 117 assigns the same data symbol to subcarriers M, M + 1, M + 2, ..., M + 9, where M is different from N. Preferably, the two subcarrier subsets do not overlap, ie, N is greater than 10 in M. Indeed, in order to increase frequency diversity, in many embodiments the same data symbol is separated as far as possible in the frequency domain, so it is desirable that the difference between N and M increase as much as possible in view of other design parameters and criteria. .

Further, the first symbol generator 115 is arranged to assign a second subset of the data symbol set to a second subset of the subcarrier of the first OFDM signaling symbol, and the second symbol generator 117 is configured to assign the first symbol of the data symbol. Assign two subsets to the first subset of carriers. Therefore, the first and second subsets of data symbols in the SIG-N field simply exchange subcarriers between two OFDM signaling symbols.

2 illustrates a specific example of data symbol assignment to an OFDM signaling symbol in accordance with some embodiments of the present invention.

In an example, multiple P subcarriers are used for each OFDM symbol and all available subcarriers of the OFDM signaling symbol are used to transmit the SIG-N field. According to the proposal for the IEEE 802.11 technical specification, P = 54 in the 20 MHz band and P = 108 in the 40 MHz band.

In the above example, data symbols continuously transmitted on the first P / 2 data subcarrier for the first OFDM signaling symbol are allocated to data carriers # P / 2 + 1 to # P / 2 for the second OFDM signaling symbol. do. Similarly, a symbol transmitted on data subcarriers # P / 2 + 1 to #P for a first OFDM signaling symbol is transmitted on a first P / 2 data subcarrier for a second OFDM signaling symbol.

3 illustrates an OFDM receiver 300 in accordance with some embodiments of the present invention.

The OFDM receiver 300 includes an antenna 301 connected to a receiver 303 that receives a signal from the OFDM transmitter 100 of FIG. 1. The receiver 303 demodulates, amplifies, and downconverts an OFDM symbol by applying a Discrete Fourier Transform (DFT), as is known to those skilled in the art.

The receiver 303 is coupled to a symbol extractor 305 which is further coupled to the first symbol processor 307, the second symbol processor 309 and the user data decoder 311. The symbol extractor 305 extracts another OFDM symbol from the data packet and specifically forwards the first OFDM signaling symbol to the first symbol processor 307 and the second OFDM signaling symbol to the second symbol processor 309. . In addition, the user data OFDM symbol is fed to the user data decoder 311.

The first symbol processor 307 processes the first OFDM signaling symbol, or the second symbol processor 309 processes the second OFDM signaling symbol such that the corresponding data symbols of the first data symbol set are two OFDM symbols. To be aligned to. For example, the second symbol processor 309 simply reorders the data of the second OFDM signaling symbol to be the same as the first OFDM signaling symbol.

The first symbol processor 307 and the second symbol processor 309 are coupled to a combiner 313 that combines data of the first and second OFDM signaling symbols.

In a simple embodiment, the combiner 313 performs a selective combination, where the combiner 313 for each subcarrier selects the data symbol value of either the first or second OFDM signaling symbol. The combiner selects, for example, the data symbol with the highest received signal value.

In other embodiments, a more advanced combination is applied, in particular the maximum ratio combination that is weighted according to a quality measure (e.g., signal to noise ratio) before each data value is added together to produce a combined data value. This applies.

Combiner 313 is coupled to receive controller 315 where the combined data values are fed. Therefore, in a particular example, the reception controller 315 receives a SIG-N field that reflects a transmission parameter used by the OFDM transmitter 100 to transmit user data.

The reception controller 315 is coupled to the user data decoder 311 and feeds information of the applied physical layer transmission parameter to the user data decoder 311. In response, the user data decoder 311 decodes the received OFDM user data symbol. For example, the user data decoder 311 applies an appropriate forward error correction decoding scheme and proceeds to decode the resulting data according to the symbol placement defined by the SIG-N field.

In the above examples, a single transmit / receive antenna has been used for communication. However, in, for example, IEEE 802.11n applications, multiple transmit and / or receive antennas may be used.

In particular, SIG-N OFDM data symbols can be transmitted through a plurality of transmit antennas, in particular using a cyclic delay diversity (CDD) scheme. 4 and 5 illustrate examples of a data packet structure for transmission according to some embodiments of the present invention applied to an IEEE 802.11n system. FIG. 4 shows an example in which two transmit antennas are employed, and FIG. 5 shows an example in which four transmit antennas are employed.

In some embodiments, the first OFDM signaling symbol further includes an indication of whether the data packet includes a second OFDM signaling symbol. Therefore, in an IEEE 802.11n communication system, some data packets are transmitted in two OFDM signaling symbols, while other data packets are transmitted in only one OFDM signaling symbol. In such a system the OFDM receiver evaluates the first OFDM signaling symbol and evaluates whether it includes an indication of the presence of the second OFDM signaling symbol. Otherwise, the receiver proceeds to determine SIG-N data based only on the first OFDM signaling symbol, otherwise proceeds to combine the signals from the two OFDM symbols. This approach allows simple determination to determine whether the SIG-N field is transmitted in one or two OFDM symbols.

The described embodiments provide substantial advantages over conventional approaches. In particular, they may allow for improved communication of the SIG-N field in an IEEE 802.11 communication system and may allow for increased communication range and thus improved coverage.

6 shows simulation results for error performance for an OFDM system, in accordance with an OFDM system, in accordance with the described embodiment. The performance is compared with the conventional transmission of a single SIG-N field and the system according to the current proposal for transmitting the SIG-N field in two OFDM symbols using BPSK modulation. Simulations were performed on channel model D in accordance with the IEEE 802.11 specification. As shown, an improvement of about 1 dB is achieved, which translates to an increase in coverage area of about 7% when compared to repeated transmissions of the SIG-N field, and 4 dB (30%) when compared to a single transmission of the SIG-N field. Improvements corresponding to increased coverage) are achieved.

Although the previous description focused on the embodiment in which two OFDM signaling symbols including a data symbol set are transmitted, it is obvious that the concepts and principles described apply equally to three or more OFDM signaling symbols transmitted.

It is obvious that the above description has described embodiments of the present invention with reference to other functional units and processors for clarity. However, it will be apparent that any suitable distribution of functionality between different functional units or processors may be used without reducing the present invention. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Therefore, references to specific functional units may only be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or configuration.

The invention may be implemented in any suitable form including hardware, software, firmware or any combination thereof. The invention may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The components and components of embodiments of the present invention may be implemented in any suitable manner physically, functionally and logically. Indeed, the functionality may be implemented as part of one unit, a plurality of units or another functional unit. As such, the invention may be implemented in one unit or may be physically and functionally distributed between other units and processors.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Additionally, although one feature may appear to be described in connection with particular embodiments, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term comprising does not exclude the presence of other elements or steps.

In addition, although individually listed, a plurality of means, components or method steps may be implemented by, for example, one unit or processor. In addition, although individual features may be included in other claims, they may be advantageously combined, and inclusion in other claims does not imply that the combination of features may be feasible or beneficial. Also, the inclusion of one feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories as well. Moreover, the order of features in the claims does not imply any particular order in which the features must be acted upon, and in particular the order of individual steps in the method claims does not imply that the steps should be performed in this order. Rather, the steps may be performed in any suitable order. In addition, a single reference does not exclude a plurality. Therefore, references to "one", "first", "second", and the like do not assume a plurality.

Claims (17)

In the Orthogonal Frequency Division Multiplexing (OFDM) transmitter, Means for generating a data symbol set indicative of a physical layer characteristic of a data transmission from the OFDM transmitter; First symbol generation means for generating a first OFDM signaling symbol by assigning the data symbol set to a subcarrier of a first OFDM signaling symbol; Second symbol generation means for generating a second OFDM signaling symbol by assigning the data symbol set to a subcarrier of a second OFDM signaling symbol, the allocation of the data symbol set to a subcarrier being the first OFDM signaling symbol and the Different for the second OFDM signaling symbol-and Transmitter means for transmitting a message comprising the first OFDM signaling symbol and the second OFDM signaling symbol OFDM transmitter comprising a. The method of claim 1, The first symbol generating means assigns a first subset of the data symbol set to a first subset of subcarriers of the first OFDM signaling symbol, and the second symbol generating means is a first sub of the data symbol set OFDM transmitter assigning the set to a second subset of subcarriers. The method of claim 2, The first symbol generating means assigns a second subset of the data symbol set to a second subset of the subcarrier of the first OFDM signaling symbol, and the second symbol generating means is a second sub of the data symbol set OFDM transmitter assigning the set to a first subset of subcarriers. The method of claim 3, And the first and second subsets of the subcarriers are non-overlapping. The method of claim 2, And said second symbol generating means assigns said first subset of data symbols to a subcarrier having a predetermined offset relative to said first subset of carriers. The method of claim 5, The second symbol generating means is configured such that one data symbol of the first subset data symbols assigned to the subcarrier number n by the first symbol generating means is assigned to the subcarrier number n + N (N is a predetermined integer). An OFDM transmitter for allocating data symbols to subcarriers. The method of claim 1, And said first symbol generating means comprises an indication of the presence of said second OFDM signaling symbol in said first OFDM signaling symbol. The method of claim 1, Wherein the message comprises an OFDM user data symbol, wherein the data symbol set indicates a physical layer transmission characteristic for the OFDM user data symbol. The method of claim 1, And said transmitter means transmits a message on a plurality of transmit antennas. The method of claim 1, And said first symbol generating means includes an indication of the allocation of said data symbol to a subcarrier in said first OFDM signaling symbol. The method of claim 1, And said OFDM transmitter is an IEEE 802.11 transmitter. An OFDM receiver for receiving a signal from an orthogonal frequency division multiplexing (OFDM) transmitter, the OFDM receiver comprising: Means for receiving a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol, the first OFDM signaling symbol representing a physical layer characteristic of a data transmission from an OFDM transmitter assigned to a subcarrier of the first OFDM signaling symbol A data symbol set including a data symbol set, wherein the second OFDM signaling symbol includes a data symbol set assigned to a subcarrier of the second OFDM signaling symbol, and the allocation of the data symbol set to a subcarrier comprises: the first OFDM signaling symbol And different for the second OFDM signaling symbol; and Means for receiving the data symbol set by combining the data symbol set of the first OFDM signaling symbol and the second OFDM signaling symbol OFDM receiver comprising a. The method of claim 10, And said receiving means combines a data symbol set of said first OFDM signaling symbol and said second OFDM signaling symbol in a maximum ratio combination. The method of claim 11, Means for detecting the presence indication of the second OFDM signaling symbol in the first OFDM signaling symbol, And the receiving means receives the data symbol set in response to the detection. The method of claim 14, And the receiving means receives the first set of data symbols without considering the second OFDM signaling symbol when the presence indication of the second OFDM signaling symbol is not detected in the first OFDM signaling symbol. An OFDM transmission method from an orthogonal frequency division multiplexing (OFDM) transmitter, Generating a data symbol set indicative of a physical layer characteristic of a data transmission from the OFDM transmitter; Generating a first OFDM signaling symbol by assigning the data symbol set to a subcarrier of a first OFDM signaling symbol; Generating a second OFDM signaling symbol by assigning the data symbol set to a subcarrier of a second OFDM signaling symbol, wherein the allocation of the data symbol set to a subcarrier is performed by the first OFDM signaling symbol and the second OFDM signaling symbol. Different for-W, Transmitting a message comprising the first OFDM signaling symbol and the second OFDM signaling symbol OFDM transmission method comprising a. A method of receiving an OFDM transmission from an orthogonal frequency division multiplexing (OFDM) transmitter, the method comprising: Receiving a message comprising a first OFDM signaling symbol and a second OFDM signaling symbol, wherein the first OFDM signaling symbol is indicative of a physical layer characteristic of a data transmission from an OFDM transmitter, assigned to a subcarrier of the first OFDM signaling symbol A data symbol set including a data symbol set, wherein the second OFDM signaling symbol includes a data symbol set assigned to a subcarrier of the second OFDM signaling symbol, and the allocation of the data symbol set to a subcarrier comprises: the first OFDM signaling symbol And different for the second OFDM signaling symbol; Receiving the data symbol set by combining the data symbol set of the first OFDM signaling symbol and the second OFDM signaling symbol OFDM receiving method comprising a.

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